数控恒流源。51单片机设计的，可以直接仿真，注解详细。- The paper expounds the design of the numerical controlled constant-Current source.　　The system core is AT89s52.The A/D D/A V/I converts and the specific arithmetic is used to carry out high precision and the current output range from 20mA to 2000mA.The source realizes that the output current can be set, 1mA adjusted step by step, the display of the present value and the practice measure value。